In my previous U.S. Pat. Nos. 3,851,995 and 4,208,665, there is disclosed apparatus for drawing a dynamometer card which is related to the pumping characteristics of a pumpjack unit. The apparatus includes means for measuring the tension in the sucker rod string by the provision of a spring loaded device which advantageously measures the force required to spring the bridle cables out of parallel relationship respective to one another.
It is known to utilize a load cell for weighing a mass. The modern load cell is usually a wheatstone bridge arranged in compact formed so that when the cell is placed in compression, a signal is generated proportional to the compressive force imposed upon the cell. The load cell is accurate, compact, relatively low in cost, and provides reliability.
The present invention discloses a load cell placed in compression by springing the bridle cables of a pumpjack unit towards one another so that the tension in the rod string can be indirectly measured in a fast and reliable manner.